1. Background of the Invention
This invention relates to a method of producing high-security, monolithic identification (ID) cards and cards made by the method.
2. Description of the Prior Art
The use of ID cards is growing in importance all over the world for use as driving licenses, financial transactions or bank cards, national ID cards, student cards, passports, security clearance cards, etc. Considering the ease by which some cards can be made, there is a need for a high-security card made using advanced technology which cannot be tampered with or forged.
There are usually two types of "printing" on ID cards. The first type of printing involves a "background" printing made up of reference and security information. The reference information may include, for example, the issuing agency, as well as other numerical data. The security information may be in the form of a watermark, an encoded magnetic strip, numerical sequences, a holographic image, etc. The second type of printing is made up of "personalized" information, such as a photographic, fingerprint, signature, name, address, etc.
One of the systems currently available makes use of a sequential or simultaneous multiple photographic exposure of both the background and personalized information by using conventional photography. There are problems with this system in that it is a wet process, it involves centralized processing so that the card is not available "instantly", and it is not a high-security system, since ordinary photography is used and such materials and skills are easily duplicated.
Another available system involves printing the background information either before or after a photograph is affixed. There are problems with this system also. If a photograph is laminated onto the surface of the ID card, then it can be altered by merely replacing the photograph. If the photograph is part of the card stock itself, then the printing of the background information is difficult since it is hard to print over the photographic gelatin surface of the card stock. Also, if a mistake is made in the printing, then the photograph has to be retaken. In addition, the system is a wet process and ia not available "instantly".
Another available system of the type described in U.S. Pat. No. 4,808,509 by Vervloet, et al, involves printing the background information on a paper support, using the diffusion transfer method to obtain the personalized information such as a photograph on another support, and then transferring the photograph onto the paper support. There are the same problems of alteration and wet processing with this system as described above.
Another available system uses conventional lithographic printing of background information on paper, followed by an electrophotographic process to obtain the personalized information or photograph. The photographs obtained by this system are usually black-and-white, however, are not continuous tone and are generally of poor quality.
A further system disclosed in U.S. Pat. No. 4,999,065 to Wilfert, incorporated herein by reference in its entirety, employs a data scanner and video camera coupled to a computerized image formatting system to operate a laser printer to print personalized and background information bearing ID cards. The paper image receiver is laminated between polyester sheets under heat and pressure in the conventional manner.
In recent years, thermal transfer system have been developed to obtain prints from pictures which have been generated electronically from a color video camera. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separated images are then converted into electrical signals. These signals are then operated on to produce cyan, magenta and yellow electrical signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor is placed face-to-face with a dye-receiver. The two are then inserted between a thermal printing head and platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor. The thermal printing head has many heating elements and is heated up sequentially in response to the cyan, magenta and yellow data print signals. The process is then repeated for the other two colors. A color image copy is thus obtained which corresponds to the original picture viewed on a screen. Further details of this process and an apparatus for carrying it out are contained in U.S. Pat. No. 4,621,271 by Brownstein, the disclosure of which is hereby incorporated by reference.
The use of the above process to produce ID cards is described in commonly assigned U.S. Pat. No. 4,738,949 by Sethi et al and U.S. Pat. No. 4,713,365 by Harrison, the disclosures of which are hereby incorporated by reference. The '949 patent discloses a high security identification card obtained by thermal dye-transfer of the personalized information, such as a photograph, signature and vital statistics on an image receiver which was previously printed with background information and thereafter laminating the image-bearing surface with a transparent laminate employing the adhesives disclosed in the '365 patent. The background information includes fine-line indicia. After lamination, it was found that attempts to delaminate or peal the double laminated composite apart caused the thermally-transferred dye image to be lifted off the polycarbonate dye-receiver layer by virtue of the strong adhesion provided by the adhesives disclosed in the '365 patent.
Various exemplary compositions are set forth in the '949 and '365 patents for the thermal-transfer dye donors, dye receivers, laminates and adhesives. As described therein, the dye receiving element of the ID card described in the '949 and '365 patents comprises a support having a dye image-receiving layer thereon which is pre-printed with fine lines. In the preferred embodiment, a polycarbonate dye image-receiving layer is employed that is coated onto a support sheet preferably polyester with a white pigment incorporated therein. The reflective support sheet and the overlying, thermally dye-transfer image bearing polycarbonate sheet are laminated between polyvinyl chloride (PVC) sheets, using the adhesives disclosed in the '365 patent.
The lamination of the support sheet between PVC sheets using such adhesives and heat and pressure is satisfactory in producing an ID card where the personalized and background information are both printed on the same polycarbonate surface and the information is to be viewed against the opaque background provided by the support sheet. However, the incorporation of the support sheet into the card renders the card susceptible to being de-laminated and altered.
It is thus desirable to increase tamper resistance by pre-printing the background information on card stock, e.g., PVC sheet material and separately print the personalized information on the exposed surface of the polycarbonate receiver sheet, which is adhered to a polyester or paper support during thermal dye-transfer printing. When the personalized image bearing surface is adhered to the PVC sheet stock, the paper support sheet must be removed so that the background and personalized information may be seen. It is undesirable to directly expose the paper support sheet to the heat and pressure of the laminating equipment, for it will become even more firmly attached to the polycarbonate sheet. On the other hand, the paper sheet must be firmly attached to the polycarbonate layer in order to support it during thermal dye-transfer printing.